Insects: Indicators and agents of global change?

Abstracts

Emma Despland: Insect outbreaks: One of the ways a changing climate transforms ecosystems

Insect outbreaks are one of the natural disturbances that renew and rejuvenate boreal forests. However, unprecendented outbreaks are now occurring far beyond their historical distribution and transforming landscapes beyond recognition.  This inceased severity, duration or geographic extent of insect outbreaks is linked to a warmer climate that favors insect development and overwinter survival.

In ecological science, a tipping-point is said to occur when an ecosystem has changed so much that it crosses a threshold at which it abruptly shifts to a different state.  It remains unclear whether climate-enhanced insect outbreaks will lead to tipping-points in boreal forests, as ecosystems that are no longer suited to the present climate transform, through the action of herbivorous insects, into novel ones.

J. Ibarra-Isassi, I. T. Handa, A. Arenas-Clavijo, S. Escobar-Ramirez, I. Armbrecht & J.-P. Lessard: I drink my coffee in the shade: Multidimensional assessment of two contrasting coffee agroecosystem management practices

Anthropogenic disturbance causes changes in species composition relative to adjacent natural patches and reduces their biotic heterogeneity. Furthermore, land use management can influence changes in biodiversity beyond the targeted species. In the last decades, management practices in coffee plantations have come from traditional practices where coffee was grown below accompanying (shade) trees, to intensified monocultures in which coffee plants grow exposed to the sun. Previous studies have shown that the latter is a major driver of biodiversity loss and associated ecosystem services. On the other hand, shade trees can act as potential shelters and facilitate dispersal of organisms, mitigating biodiversity and ecosystem service loss. In our study, we assessed the impact of coffee plantation management practices on the taxonomical, phylogenetic and functional composition of ant communities, an ecologically dominant group and crucial biological pest controller in these agroecosystems. We compared the composition of ant communities found in 8 sun-grown plantations and 8 shade-grown plantations with 8 nearby forest patches in the mountains of southern Colombia. Our results show that sun-grown coffee plantations change taxonomic, phylogenetic and functional composition of ant communities when compared to forest patches or shade-grown plantations. Additionally, we find that sun-grown plantations taxonomically and functionally homogenize ant communities, but not at the phylogenetic level. Our results indicate that pluralistic approaches for characterizing the changes of biodiversity in agroecosystems can be used to better inform land management strategies focusing on minimizing biodiversity and ecosystem service loss. Moreover, our findings provide evidence for traditional practices buffering the impoverishment of multiple diversity facets after forest conversion.

Pamelia Yataco: Plantation and mixed-wood forest

Defoliating insects cause great losses to Picea Glauca lumber production of Canada. To identify the most damaging herbivorous arthropod species we studied community composition in plantations and natural mixed wood sites. Damage on spruce was classified by the arthropod that caused it. Results showed that both communities differed significantly in their composition. The pattern was driven by high abundance of aphid from the genus Cinara and a Pale spruce adelgids, Adelges abietis, in plantation sites. This pattern persisted when analyzing the ordination of the functional traits and phylogenetic differences amongst sites. Lepidopterans thus seem to do less well in young plantation trees than in forest, which may be caused by various factors such as predation and abiotic factors.